Precision axle spindle and wheel end assembly for heavy-duty vehicles

Abstract

An axle spindle and wheel end assembly includes a precision-formed axle spindle, wheel hub, and axle spindle nut. The axle spindle is formed with parallel inboard and outboard bearing surfaces, a shoulder that is perpendicular to the inboard and outboard bearing surfaces, and threads for a spindle nut that are aligned with the inboard and outboard bearing surfaces. The wheel hub is formed with inboard and outboard bearing surfaces that are in parallel alignment with one another, and bearing axial stop surfaces that are perpendicular to the wheel hub bearing surfaces. The spindle nut is formed with threads on its inner periphery and a flat inboard surface that is perpendicular to the threads. The axle spindle, wheel hub, and spindle nut cooperate to enable an axle spindle nut assembly to consistently provide a light preload on a bearing cone and spacer group of the wheel end assembly.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional of U.S. application Ser. No. 12 / 790,054, filed on May 28, 2010, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61 / 182,277, filed on May 29, 2009.BACKGROUND OF THE INVENTION[0002]1. Technical Field[0003]The invention relates to vehicle axles and wheel end assemblies, and in particular to axles and wheel end assemblies for heavy-duty vehicles, such as tractor-trailers. More particularly, the invention is directed to a heavy-duty axle spindle and wheel end assembly that includes a precision-formed axle, wheel hub, and axle spindle nut which cooperate to enable the axle spindle nut to achieve a precise position and thus provide a desirable light preload on the bearings of the wheel end assembly.[0004]2. Background Art[0005]For many years, the heavy-duty vehicle industry has utilized wheel end assemblies which are mounted on each end of one or more non-drive axles. Each wheel end assem...

AI Technical Summary

Benefits of technology

The solution enables repeatable and precise positioning of the axle spindle nut, achieving a light preload condition that extends bearing and seal life, reduces maintenance costs, and minimizes axial end play, while using lower tightening torques compared to prior art systems.

Problems solved by technology

Therefore, the wheel end assembly also must be sealed to prevent leakage of the lubricant, and also to prevent contaminants from entering the assembly, both of which could be detrimental to its performance.

Moreover, the design and construction of prior art axle spindles, wheel hubs and axle spindle nuts exhibit certain disadvantages associated with installation and maintenance of an optimum position of the spindle nut to provide the proper clamp force to compress the bearings.

For example, if the position of the axle spindle nut does not create a sufficient clamp force on the bearing cone and spacer group, there may be excessive end play of the bearings, which in turn creates excessive axial end play of the wheel end assembly relative to the axle spindle.

Such excessive end play may allow undesirable movement of the main seal, which in turn potentially reduces the life of the main seal and the bearings.

If the position of the axle spindle nut creates a clamp force on the bearing cone and spacer group that is too high, the bearings may effectively be over-compressed, interfering with their rotation and causing them to potentially wear out prematurely.

However, placing a light preload on the bearing cone and spacer group involves a very narrow and precise range of clamp force, which requires an extremely precise position of the axle spindle nut, making the light preload condition extremely difficult to achieve and maintain.

In the prior art, the development of components that can consistently and reliably create a uniform light preload condition has not been accomplished.

This has been due primarily to the lack of a precision-formed axle, wheel hub, and axle spindle nut which cooperate to enable the spindle nut to consistently achieve and maintain a precise position, and thus a light preload condition.

As a result, manufacturers have instead designed axle spindle and wheel end assemblies to employ a position of the axle spindle nut that results in a certain amount of axial end play, having determined that, while not optimal, it is a more desirable condition than a position of the axle spindle nut which results in a clamp force that over-compresses the bearings.

For example, on prior art axle spindle and wheel end assemblies that employ wheel hubs with high-end, specialized unitized bearings or bearing cartridge systems, undesirably high tightening torques in excess of 500 foot-pounds are required.

Such high torques do not allow consistent repeatability of a precise axle spindle nut position and thus a proper clamp force that is able to maintain a light preload condition.

These assemblies have a moderate tightening torque, but the tolerances associated with the manufacturing of the bearing spacer preclude the repeatable precision that is needed to achieve a light preload condition.

However, the optimum bearing fatigue life is not obtainable using such a wheel hub in conjunction with an axle spindle nut position that allows axial end play.

In addition, if a clamp force that achieves a light preload is attempted with such a hub, it is likely that the bearings will inadvertently be overloaded or over-compressed due to non-uniform loading caused by the aforementioned misalignment of the bores of the bearing surfaces.

In addition, the prior art forming processes for axle spindles contribute to the lack of precision of the system.

Friction welding the axle spindle to the axle central tube may create variation in alignment of the opposite spindles on the axle, which results in the spindle threads being tipped or out of alignment relative to the bearing surfaces on the spindle.

However, if a clamp force that achieves a light preload is attempted, it is likely that the bearings will inadvertently be overloaded or over-compressed due to non-uniform loading caused by the misalignment of the axle spindle threads to the spindle bearing surfaces.

More particularly, axle spindle nuts typically do not include threads that are accurately or precisely positioned perpendicular to the inboard surface of the nut, due to separate machining processes and / or separate locating surfaces for machining the inboard surface of the nut and for forming the threads in the nut.

As a result, prior art axle spindle and wheel end assemblies lack the necessary precision on the critical surfaces of the axle spindle, wheel hub and axle spindle nut to enable the axle spindle nut to achieve a precise position and thus in turn achieve a consistent, desirable light preload condition in clamping the bearing cone and spacer group of the wheel end assembly.

These disadvantages of prior art axle spindle and wheel end assemblies make it desirable to develop a heavy-duty axle spindle and wheel end assembly that includes a precision-formed axle, wheel hub, and axle spindle nut which cooperate to enable the axle spindle nut to consistently achieve a precise position and thus provide a light preload on the bearing cone and spacer group of the wheel end assembly.

Images